var xmlHttp

function checkUser(str)
{ 
	document.getElementById("userValidate").innerHTML=""; 
	if (str == "")
	{
		alert ("Nothing entered in username field.");
		return;
	}
	
	xmlHttp=GetXmlHttpObject();
	if (xmlHttp==null)
	{
		alert ("Browser does not support HTTP Request");
	 	return;
	}
	var url="checkuser.php"
	url=url+"?u="+str
	url=url+"&sid="+Math.random()
	xmlHttp.onreadystatechange=stateChanged;
	xmlHttp.open("GET",url,true);
	xmlHttp.send(null);
}

function stateChanged() 
{ 
	if (xmlHttp.readyState==4 || xmlHttp.readyState=="complete")
 	{ 
 		document.getElementById("userValidate").innerHTML=xmlHttp.responseText ;
 	} 
}

function GetXmlHttpObject()
{
	var xmlHttp=null;
	try
	{
	 	// Firefox, Opera 8.0+, Safari
	 	xmlHttp=new XMLHttpRequest();
	}
	catch (e)
	{
	 //Internet Explorer
	 	try
	  	{
	  		xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
	  	}
	 	catch (e)
	  	{
	  		xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
	  	}
	}
	return xmlHttp;
}